From MozillaZine Knowledge Base
Mozilla Suite and Firefox store the disk cache in the "Cache" directory located in the profile folder or, in SeaMonkey and Firefox 1.5 and above, in the "profile temp directory" . The Cache directory location can be viewed in about:cache.
The Cache location can be changed by adding the "browser.cache.disk.parent_directory" preference and entering a folder path. (In the past, this was specified in the "browser.cache.disk.directory" preference and before that, "browser.newcache.directory" and "browser.cache.directory" behaved similarly.) Once this preference is specified, a new directory named “Cache” will be created at the path you set, upon browser restart.
Note: In Windows, if the "browser.cache.disk.parent_directory" value is being set in the prefs.js or user.js file instead of about:config, the path separator must be two backslashes (e.g., "C:\\Path\\To\\Parent").
Possible values and their effects
Any path with full write permissions by the current user is considered valid. As mentioned above, the actual disk cache contents will be stored in a directory beneath this path.
Mozilla Suite and SeaMonkey
A “Choose Folder” button is available under “Edit → Preferences → Advanced → Cache”.
A fast, local hard disk is the best choice for storing your disk cache files. If you’re concerned about privacy, you may want to look into creating a RAM disk and using that as the location for your cache.
First checked in
Has an effect in